Cleaning creosote



Patented Jan. 9, 1945 CLEANING CREOSOTE Victor F. Hribar, Chicago, Ill., assignor to American Lumber & Treating 00., a corporation of Delaware 'No Drawing. Application July 10, 1942, Serial No. 450,493

6 Claims.

use.

The most troublesome impurity is the increase in the so-called coke residue and matter insoluble in benzol. Most of the coke and benzol insolubles are forms of carbon, although a small amount may be dirt, wood fibre, resins, etc. The

impurities are classified as insoluble A, insoluble B and insoluble 0. They are due to the use of pressure. temperature, the presence of wood resins, moisture, oxygen, etc., encountered un-- der normal impregnation schedules. ioan Wood-preservers Association specification and other treating standards limit the coke residue and benzol insoluble because these may interfere with good creosote treatment. For instance, the AWPA specification for grade 1 creosote (Manual Standard 4]) states: It shall not contain more than 0.5% of matter insoluble in benzol but it carries the following footnote, Samples of creosote taken from working tanks may show an increase in matter insoluble in benzol due to treating operations. Such increases provided they do not exceed by 1% the specification limits should not serve to cause rejection of the creosote for non-conformity with specifications if it can be shown that the original fresh oil was of specified quality. The foregoing evidences the change; however, once past the 1% tolerance it is necessary to clean the creosote.

The term cleaning creosote is used in the industry to mean the removal of carbon and other insolubles.

In general, more weight is given to the benzol insoluble test than the coke residue test.

Creosote is a distillate of coal-tar produced by high temperature carbonization of bituminous coal; it consists principally of liquid and solid aromatic hydrocarbons and contains appreciable quantities of tar acids and tar bases; it is heavier than water; and has a continuous boiling range of at least 125 (2., beginning at about 200 C. It is not a single chemical, but a mixture containing a great number of compounds which may include phenols, cresols, xylenols, and naphthols, pyridines, acridines, benzene, toluene, xylene,

The Amer- .4

naphthalene, anthracene, and many others. It is evident that creosote is closely associated with carbon and other complex compounds.

At the present time the common methods to remove coke residue and benzol insoluble are by filter press or centrifuge.

The data in the AWPA Proceedings show that creosote with a 1.35 per cent benzol may be filtered to a 0.81 per cent benzol insoluble or centrifuged to a 0.56 per cent benzol insoluble. It has been further shown that certain of the benzol insolubles are also water soluble and may or may not be fully removed by present cleaning methods.

Both the filter press and the centrifuge have certain disadvantages. The centrifuge handles onlysmall volumes of creosote and must be attended almost constantly. The filter press is a very dirty operation and it requires practically a water-free creosote which is difficult to obtain. Both processes are comparatively expensive.

The fact is well known that part of the creosote fractions known as the benzol insoluble will settle if permitted to stand without agitation. This accounts for sludge in storage and working tank bottoms; however, this rarely accomplishes sufiicient benzol insoluble removal to be considered as creosote cleaning. 1

It has now been discovered that materials used in the mining industry as depressants in connection with water solutions of ore may likewise be employed to produce more rapid and complete precipitation of carbon and other insolubles from creosote to such an extent that inexpensive and thoroughly satisfactory cleaning of the creosote may be accomplished with small percentages of the depressants.

The depressants used in the mining industry Y comprise a rather wide class including alkali metal cyanides or other soluble cyanides, zinc sulphate, sodium phosphite, starch and the alkali metal dichromates.

deposited in the KMnOr test is as follows. In feebly acid, neutral, or alkaline solutions the ,septa-valent manganese is reduced to the quadrivalent state, thus causing the precipitation of hydrated manganese dioxide.

Reducing substances in creosote will react with. the permanganate to form manganese dioxide.

7 The reduced form of manganese dioxide has a specific gravity of than one-fourth of one per cent. Larger amounts than one per cent may be employed but 'they are generally unnecessary and uneconomical.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom.

What I claim as new, and desire to secure by Letters Patent is:

1. The method of cleansing creosote from insoluble impurities which comprises maintaining creosote which has become dirty in the treatment of forest products in a quiescent state in the presence of at least approximately 0.25% and not substantially more than 1% by weight of a depressant of the class consisting of alkali metal permanganates, and alkali metal dichromates.

2. The method of cleansing creosote which comprises adding thereto a small amount not less than 0.25% of potassium permanganate and maintaining the dirty creosote quiescent until a substantial proportion of the impurities has settled therefrom.

3. The method of cleansing creosote which has acquired insoluble'forest product impurities in excess of 1.5% of material insoluble in benzol through the treatment of forest products, which comprises adding to a quiescent bath of dirty creosote not substantially less than 0.25% and not substantially more than 1% of an alkali metal permanganate, maintaining the mixture quiescent for an extended period during which matter insoluble in benzol settles to reduce the content thereof in the creosote to less than 1%.

4. The method of cleansing creosote which has acquired insoluble forest product impurities in excess of 1.5% of material insoluble in benzol through the treatment of forest products, which comprises adding to a quiescent bath of dirty creosote not substantially less than 0.25% and not substantially more than 1% of potassium permanganate, maintaining the mixture quiescent for an extended period during which matter insoluble in benzol settles to reduce the content thereof in the creosote to less than 1%.

5. The method of cleansing creosote which has acquired insoluble forest product impurities in excess of 1.5% of material insoluble in benzol through the treatment of forest products, which comprises adding to a quiescent bath of dirty creosote not substantially less than 0.25% and not substantially more than 1% of alkali metal dichromate, maintaining the mixture quiescent for an extended period during which matter insoluble in benzol settles to reduce the content thereof in the creosote to less than 1%. p

6. The method of cleansing creosote which has acquired insoluble forest product impurities in excess of 1.5% of material insoluble in benzol through the treatment of forest products, which comprises adding to a quiescent bath of ciirty creosote not substantially less than 0.25% and not substantially more than 1% of potassium di- VICTOR F. I-IRIBAR. 

